Abstract
Introduction: In severe COPD patients, exercise tolerance is mainly limited by ventilation. The application of a pressure support (PS) during exercise has proven successful to increase exercise endurance and reduce symptoms as well as to improve the benefit of rehabilitation.
We wondered whether the extent of quadriceps fatigue following a cycling exercise could be prevented by the application of PS.
Methods: We studied severe COPD patients with a poor exercise tolerance during the cardiopulmonary exercise test. We measured endurance of the quadriceps (TlimQ) during isotonic knee extension at 70% of 1RM, as a control test. Thereafter on 2 separate days, before performing TlimQ, the patients performed an endurance cycling test, while breathing ambient air (AA) or with PS (Elisee 250, ResMed, France).
Results: We have included 20 patients (63.2±8.6 yrs old, BMI 27.3±6.3 kg.m−2, FEV1 39.9±19.9% pred, maximal workload 34.5±19.8% pred).
The cycling exercise test with AA was associated with a 24.5±21.1% decrease of TlimQ (P=0.0004). By contrast, application of the PS partly prevented the TlimQ reduction (−7.5±16.7%, NS). After cycling exercise, the patients experienced less fatigue with PS than with AA (Borg score = 4.0±2.6 versus 2.7±1.8, p<0.008), and reduced dyspnea (Borg score = 4.3±2.5 versus 3.2±2.1, p<0.02).
Conclusion: The application of PS during exercise in severe COPD patients prevents quadriceps fatigue, as assessed by a quadriceps endurance test. This suggests that the reduction of respiratory work influences peripheral muscle function. It remains to determine whether this reduction of muscle fatigue allows to increase workload during the exercise training sessions.
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